Skip to content

Commit

Permalink
Allow usage of signal names
Browse files Browse the repository at this point in the history 
- Adds a mapping of signal numbers to signal names based on the "most common" (subjective) signals.
- This allows the same config/script to be used on different platforms, for example: -r TERM:QUIT (15:3 on Linux vs. 25:20 on OS X).
- Each entry is wrapped in a #ifdef SIG<NAME>/#endif pair in an attempt to make this implementation as portable as possible.
- Names can be specified with or without the SIG prefix, and numbers and names can be used in any combination: -r 15:3, -r TERM:QUIT, -r SIGTERM:3, -r TERM:SIGQUIT, etc.
- Corresponding signum_to_signame() and signame_to_signum() functions were added.
- A new -l/--list option shows the mapping in use on the current system/platform/OS.
- Debug output has been updated to include the signal name along with the number.

Fixes Yelp#87.
  • Loading branch information
@jhriggs
jhriggs committed May 13, 2020
1 parent 2da4dc4 commit 15abd43
Show file tree
Hide file tree
Showing 5 changed files with 242 additions and 26 deletions.
6 changes: 5 additions & 1 deletion README.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,10 @@ which always sends a standard signal (e.g. SIGTERM). Some apps require a
different stop signal in order to do graceful cleanup.

For example, to rewrite the signal SIGTERM (number 15) to SIGQUIT (number 3),
just add `--rewrite 15:3` on the command line.
just add `--rewrite 15:3` or `--rewrite TERM:QUIT` on the command line. Signal
names can be specified with or without the `SIG` prefix (e.g. `TERM` or
`SIGTERM`). To see the mapping of signal numbers to names on the system in
question, specify `-l/--list`.

To drop a signal entirely, you can rewrite it to the special number `0`.

Expand Down Expand Up @@ -218,6 +221,7 @@ ENTRYPOINT ["/usr/bin/dumb-init", "--"]

# or if you use --rewrite or other cli flags
# ENTRYPOINT ["dumb-init", "--rewrite", "2:3", "--"]
# ENTRYPOINT ["dumb-init", "--rewrite", "TERM:QUIT", "--"]

CMD ["/my/script", "--with", "--args"]
```
Expand Down
216 changes: 202 additions & 14 deletions dumb-init.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,155 @@ pid_t child_pid = -1;
char debug = 0;
char use_setsid = 1;

typedef struct signame_map_entry {
const int signum;
const char *signame;
} signame_map_entry;

static const signame_map_entry signame_map[] = {
#ifdef SIGABRT
{ SIGABRT, "ABRT" },
#endif
#ifdef SIGALRM
{ SIGALRM, "ALRM" },
#endif
#ifdef SIGBUS
{ SIGBUS, "BUS" },
#endif
#ifdef SIGCHLD
{ SIGCHLD, "CHLD" },
#endif
#ifdef SIGCONT
{ SIGCONT, "CONT" },
#endif
#ifdef SIGEMT
{ SIGEMT, "EMT" },
#endif
#ifdef SIGFPE
{ SIGFPE, "FPE" },
#endif
#ifdef SIGHUP
{ SIGHUP, "HUP" },
#endif
#ifdef SIGILL
{ SIGILL, "ILL" },
#endif
#ifdef SIGINFO
{ SIGINFO, "INFO" },
#endif
#ifdef SIGINT
{ SIGINT, "INT" },
#endif
#ifdef SIGIO
{ SIGIO, "IO" },
#endif
#ifdef SIGIOT
{ SIGIOT, "IOT" },
#endif
#ifdef SIGKILL
{ SIGKILL, "KILL" },
#endif
#ifdef SIGLOST
{ SIGLOST, "LOST" },
#endif
#ifdef SIGPIPE
{ SIGPIPE, "PIPE" },
#endif
#ifdef SIGPOLL
{ SIGPOLL, "POLL" },
#endif
#ifdef SIGPROF
{ SIGPROF, "PROF" },
#endif
#ifdef SIGPWR
{ SIGPWR, "PWR" },
#endif
#ifdef SIGQUIT
{ SIGQUIT, "QUIT" },
#endif
#ifdef SIGSEGV
{ SIGSEGV, "SEGV" },
#endif
#ifdef SIGSTKFLT
{ SIGSTKFLT, "STKFLT" },
#endif
#ifdef SIGSTOP
{ SIGSTOP, "STOP" },
#endif
#ifdef SIGSYS
{ SIGSYS, "SYS" },
#endif
#ifdef SIGTERM
{ SIGTERM, "TERM" },
#endif
#ifdef SIGTRAP
{ SIGTRAP, "TRAP" },
#endif
#ifdef SIGTSTP
{ SIGTSTP, "TSTP" },
#endif
#ifdef SIGTTIN
{ SIGTTIN, "TTIN" },
#endif
#ifdef SIGTTOU
{ SIGTTOU, "TTOU" },
#endif
#ifdef SIGUNUSED
{ SIGUNUSED, "UNUSED" },
#endif
#ifdef SIGURG
{ SIGURG, "URG" },
#endif
#ifdef SIGUSR1
{ SIGUSR1, "USR1" },
#endif
#ifdef SIGUSR2
{ SIGUSR2, "USR2" },
#endif
#ifdef SIGVTALRM
{ SIGVTALRM, "VTALRM" },
#endif
#ifdef SIGWINCH
{ SIGWINCH, "WINCH" },
#endif
#ifdef SIGXCPU
{ SIGXCPU, "XCPU" },
#endif
#ifdef SIGXFSZ
{ SIGXFSZ, "XFSZ" },
#endif
};
int signame_map_size = sizeof(signame_map) / sizeof(signame_map[0]);

const char *signum_to_signame(int signum) {
int i;

for (i = 0; i < signame_map_size; i++) {
if (signame_map[i].signum == signum) {
return signame_map[i].signame;
}
}

return NULL;
}

int signame_to_signum(const char *signame) {
int i;
const char *name = signame;

if (!strncmp(name, "SIG", 3)) {
name += 3;
}

for (i = 0; i < signame_map_size; i++) {
if (!strcmp(signame_map[i].signame, name)) {
return signame_map[i].signum;
}
}

return 0;
}

int translate_signal(int signum) {
if (signum <= 0 || signum > MAXSIG) {
return signum;
Expand All @@ -54,7 +203,7 @@ int translate_signal(int signum) {
if (translated == -1) {
return signum;
} else {
DEBUG("Translating signal %d to %d.\n", signum, translated);
DEBUG("Translating signal %d (%s) to %d (%s).\n", signum, signum_to_signame(signum), translated, signum_to_signame(translated));
return translated;
}
}
Expand All @@ -64,7 +213,7 @@ void forward_signal(int signum) {
signum = translate_signal(signum);
if (signum != 0) {
kill(use_setsid ? -child_pid : child_pid, signum);
DEBUG("Forwarded signal %d to children.\n", signum);
DEBUG("Forwarded signal %d (%s) to children.\n", signum, signum_to_signame(signum));
} else {
DEBUG("Not forwarding signal %d to children (ignored).\n", signum);
}
Expand All @@ -91,10 +240,10 @@ void forward_signal(int signum) {
*
*/
void handle_signal(int signum) {
DEBUG("Received signal %d.\n", signum);
DEBUG("Received signal %d (%s).\n", signum, signum_to_signame(signum));

if (signal_temporary_ignores[signum] == 1) {
DEBUG("Ignoring tty hand-off signal %d.\n", signum);
DEBUG("Ignoring tty hand-off signal %d (%s).\n", signum, signum_to_signame(signum));
signal_temporary_ignores[signum] = 0;
} else if (signum == SIGCHLD) {
int status, exit_status;
Expand All @@ -106,7 +255,7 @@ void handle_signal(int signum) {
} else {
assert(WIFSIGNALED(status));
exit_status = 128 + WTERMSIG(status);
DEBUG("A child with PID %d was terminated by signal %d.\n", killed_pid, exit_status - 128);
DEBUG("A child with PID %d was terminated by signal %d (%s).\n", killed_pid, exit_status - 128, signum_to_signame(exit_status - 128));
}

if (killed_pid == child_pid) {
Expand Down Expand Up @@ -137,8 +286,11 @@ void print_help(char *argv[]) {
" In this mode, signals are only proxied to the\n"
" direct child and not any of its descendants.\n"
" -r, --rewrite s:r Rewrite received signal s to new signal r before proxying.\n"
" To ignore (not proxy) a signal, rewrite it to 0.\n"
" This option can be specified multiple times.\n"
" Signals may be specified as numbers or names like USR1 or\n"
" SIGINT (see -l/--list). To ignore (not proxy) a signal,\n"
" rewrite it to 0. This option can be specified multiple\n"
" times.\n"
" -l, --list Print signal number to name mapping and exit.\n"
" -v, --verbose Print debugging information to stderr.\n"
" -h, --help Print this help message and exit.\n"
" -V, --version Print the current version and exit.\n"
Expand All @@ -153,20 +305,49 @@ void print_rewrite_signum_help() {
fprintf(
stderr,
"Usage: -r option takes <signum>:<signum>, where <signum> "
"is between 1 and %d.\n"
"is between 1 and %d, specified by number or name.\n"
"This option can be specified multiple times.\n"
"Use --help for full usage.\n",
MAXSIG
);
exit(1);
}

int scansignal(const char *arg, int min, int *pos) {
int signum, outpos;
char signame[10];

if (
sscanf(arg, "%d%n", &signum, &outpos) == 1
&& (signum >= min && signum <= MAXSIG)
) {
*pos = outpos;
return signum;
} else if (
(
sscanf(arg, "SIG%9[A-Z0-9]%n", signame, &outpos) == 1
|| sscanf(arg, "%9[A-Z0-9]%n", signame, &outpos) == 1
)
&& (signum = signame_to_signum(signame))
&& (signum >= min && signum <= MAXSIG)
) {
*pos = outpos;
return signum;
} else {
print_rewrite_signum_help();
}

return -1;
}

void parse_rewrite_signum(char *arg) {
int signum, replacement;
int signum, replacement, pos;

if (
sscanf(arg, "%d:%d", &signum, &replacement) == 2 &&
(signum >= 1 && signum <= MAXSIG) &&
(replacement >= 0 && replacement <= MAXSIG)
(signum = scansignal(arg, 1, &pos)) >= 1
&& arg[pos] == ':'
&& (replacement = scansignal(arg += pos + 1, 0, &pos)) >= 0
&& arg[pos] == 0
) {
signal_rewrite[signum] = replacement;
} else {
Expand All @@ -181,16 +362,17 @@ void set_rewrite_to_sigstop_if_not_defined(int signum) {
}

char **parse_command(int argc, char *argv[]) {
int opt;
int opt, i;
struct option long_options[] = {
{"help", no_argument, NULL, 'h'},
{"single-child", no_argument, NULL, 'c'},
{"rewrite", required_argument, NULL, 'r'},
{"list", no_argument, NULL, 'l'},
{"verbose", no_argument, NULL, 'v'},
{"version", no_argument, NULL, 'V'},
{NULL, 0, NULL, 0},
};
while ((opt = getopt_long(argc, argv, "+hvVcr:", long_options, NULL)) != -1) {
while ((opt = getopt_long(argc, argv, "+hvVlcr:", long_options, NULL)) != -1) {
switch (opt) {
case 'h':
print_help(argv);
Expand All @@ -200,6 +382,12 @@ char **parse_command(int argc, char *argv[]) {
break;
case 'V':
fprintf(stderr, "dumb-init v%s", VERSION);
exit(0);
case 'l':
for (i = 1; i <= MAXSIG; i++) {
fprintf(stderr, "%2d: %s\n", i, signum_to_signame(i));
}

exit(0);
case 'c':
use_setsid = 0;
Expand Down
20 changes: 13 additions & 7 deletions tests/cli_test.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -55,8 +55,11 @@ def test_help_message(flag, current_version):
b' In this mode, signals are only proxied to the\n'
b' direct child and not any of its descendants.\n'
b' -r, --rewrite s:r Rewrite received signal s to new signal r before proxying.\n'
b' To ignore (not proxy) a signal, rewrite it to 0.\n'
b' This option can be specified multiple times.\n'
b' Signals may be specified as numbers or names like USR1 or\n'
b' SIGINT (see -l/--list). To ignore (not proxy) a signal,\n'
b' rewrite it to 0. This option can be specified multiple\n'
b' times.\n'
b' -l, --list Print signal number to name mapping and exit.\n'
b' -v, --verbose Print debugging information to stderr.\n'
b' -h, --help Print this help message and exit.\n'
b' -V, --version Print the current version and exit.\n'
Expand Down Expand Up @@ -90,9 +93,9 @@ def test_verbose(flag):
(
'(^|\n)\\[dumb-init\\] Child spawned with PID [0-9]+\\.\n'
'.*' # child might print here
'\\[dumb-init\\] Received signal {signal.SIGCHLD}\\.\n'
'\\[dumb-init\\] Received signal {signal.SIGCHLD} \\(CHLD\\)\\.\n'
'\\[dumb-init\\] A child with PID [0-9]+ exited with exit status 0.\n'
'\\[dumb-init\\] Forwarded signal 15 to children\\.\n'
'\\[dumb-init\\] Forwarded signal 15 \\(TERM\\) to children\\.\n'
'\\[dumb-init\\] Child exited with status 0\\. Goodbye\\.\n$'
).format(signal=signal).encode('utf8'),
stderr,
Expand All @@ -111,9 +114,9 @@ def test_verbose_and_single_child(flag1, flag2):
assert re.match(
(
'^\\[dumb-init\\] Child spawned with PID [0-9]+\\.\n'
'\\[dumb-init\\] Received signal {signal.SIGCHLD}\\.\n'
'\\[dumb-init\\] Received signal {signal.SIGCHLD} \\(CHLD\\)\\.\n'
'\\[dumb-init\\] A child with PID [0-9]+ exited with exit status 0.\n'
'\\[dumb-init\\] Forwarded signal 15 to children\\.\n'
'\\[dumb-init\\] Forwarded signal 15 \\(TERM\\) to children\\.\n'
'\\[dumb-init\\] Child exited with status 0\\. Goodbye\\.\n$'
).format(signal=signal).encode('utf8'),
stderr,
Expand All @@ -129,6 +132,9 @@ def test_verbose_and_single_child(flag1, flag2):
('-r', '15'),
('-r', '15::12'),
('-r', '15:derp'),
('-r', '15:SIGBAR'),
('-r', 'TERM:SIGBAR'),
('-r', 'FOO:12'),
('-r', '15:12', '-r'),
('-r', '15:12', '-r', '0'),
('-r', '15:12', '-r', '1:32'),
Expand All @@ -144,7 +150,7 @@ def test_rewrite_errors(extra_args):
assert proc.returncode == 1
assert stderr == (
b'Usage: -r option takes <signum>:<signum>, where <signum> '
b'is between 1 and 31.\n'
b'is between 1 and 31, specified by number or name.\n'
b'This option can be specified multiple times.\n'
b'Use --help for full usage.\n'
)
18 changes: 18 additions & 0 deletions tests/proxies_signals_test.py
View file
Original file line number Diff line number Diff line change
Expand Up @@ -105,3 +105,21 @@ def test_ignored_signals_are_not_proxied():
proc.send_signal(signal.SIGWINCH)
proc.send_signal(signal.SIGHUP)
assert proc.stdout.readline() == '{}\n'.format(signal.SIGHUP).encode('ascii')


@pytest.mark.usefixtures('both_debug_modes', 'both_setsid_modes')
def test_signal_names():
"""Ensure dumb-init can map signal names."""
rewrite_map = {
'TERM': 'QUIT',
'SIGINT': 0,
'WINCH': 0,
}
with print_signals(_rewrite_map_to_args(rewrite_map)) as (proc, _):
proc.send_signal(signal.SIGTERM)
proc.send_signal(signal.SIGINT)
assert proc.stdout.readline() == '{}\n'.format(signal.SIGQUIT).encode('ascii')

proc.send_signal(signal.SIGWINCH)
proc.send_signal(signal.SIGHUP)
assert proc.stdout.readline() == '{}\n'.format(signal.SIGHUP).encode('ascii')
Loading

0 comments on commit 15abd43

Please sign in to comment.